The kerneld/GOODIES directory in
modules package has a couple of kernel patches for screen-saver
and console-beep support in kerneld; these are not yet part of
the official kernel, so you will need to install the
kernel-patches and rebuild the kernel.

When the screen-saver triggers, kerneld will run the
command /sbin/screenblanker; this file may
be anything you like, for example, a shell script that runs your
favorite screen-saver.

When the kernel wants to unblank the screen, it sends a
SIGQUIT signal to the process running
/sbin/screenblanker. Your shell script or
screen-saver should trap this, and terminate. Remember to restore
the screen to the original text mode!